Depression is killing me

I am 16 years old. I study in college. I am in 1st year. Exams will start from 28th April. My life is very depressing. My siblings live out of country. They left me when I was very young. My father spends all the time in office. My mother is a teacher. She spends half of her day in school and the remaining half with her mother and brother. We do not talk much. I had a group of six friends. We used to enjoy a lot. But then we splitted. Now I only have two friends left. I spend all my time either studying or using mobile phone. Loneliness is killing me. We have no relatives. We don't go out of house. I have no boyfriend nor do I want one. I spend mg whole day in my room listening to sad songs. There was this guy in school I liked a lot. I had these vibes coming from him. He stared me all the time. He is not cute. But I was then attracted towards him though he is a bit ugly. I used to wait for him in the academy. We splitted in college. He joined another college. Due to caste difference, he never proposed me rather proposed my best friend. This thought kills me. He is the only person I ever loved truly. The way he looked at me made me feel special. Though we never talked to each other, still there was a connection between us and it was strong until he came to know I belong to a different caste. My friend turned down his proposal. No one knows I like him except my cousin. She also likes a boy. And has exactly the same story like me. I was a topper till matric. Now I don't get good grades. I skip classes. I bunk. I remain depressed. I listen to sad songs all the time. I keep crying and praying to God. :(